Benzoquinones, from enzymatic oxidation

Artificial humic acids were produced, either chemically or enzymatically, from a variety of phenols, from sulphonated napthoquinone, and fromp-benzoquinone, together with numerous amino acids. Microbial decomposition of both natural and artificial humic acids was usually negligible. When model humic acids were prepared by reacting quinones formed from phenols, usually with amino acids present, it was observed that oxidation, polymerization, and polycondensation were more rapid in the presence of amino acids than in their absence. Evidently the amino acids participate in these reactions. Colorless products were formed initially which gradually darkened to reddish-brown and then brownish-black. These humic acids had many physical and chemical properties that corresponded closely to those of natural humic acids. 

The chemoenzymatic synthesis of (13S)-hydroxy-18 2(9Z,ll ) was achieved in nine steps starting from (2 )-octenal. Of importance was the enzymatic conversion of (2 )-octenal to the (5)-cyanohydrin [5] with (S)-hydroxynitrile lyase cloned from Hevea brasiliensis (41). 13- Hydroxy-lO-oxo-18 1(11 ) was synthesized via a Kno-evenagel-type reaction of Isopropyl 11 - phenylsulfinyl-10-oxoundecanoate with hep-tanal to form y-hydroxyenone functionality together with carbon chain elongation (42). The regiospecific oxidation of a number of substituted unsaturated fatty esters with /7-benzoquinone in the presence of palladium(II) chloride under concomitant ultrasonic irradiation was reported. For example, methyl 9-hydroxy-18 1 (12Z) furnished methyl 9-hydroxy-12-keto-18 0 exclusively (43). 

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